Current redistricting period has produced the closest relationship between votes received and seats won by party across the nation's 435 U.S. House districts since the 1940s

This is the second in a series of reports on Congressional redistricting. The first report documented how the Democratic Party has won several hundred more U.S. House seats than their proportional cumulative vote share since the 1940s, with the Republican Party receiving several hundred fewer seats.

Even as the political environment of recent years has descended more and more into one of increased partisanship and polarized parties - with liberal Republicans in the Northeast and conservative Democrats in the South becoming dying breeds - the current district lines drawn up by the 50 states in 2002 have yielded the most proportional results in the national distribution of votes received and seats won for the U.S. House since World War II.

A Smart Politics analysis of nearly 15,000 U.S. House general election returns since 1942 finds that the difference between the percentage of cumulative votes received by the Democratic and Republican Parties each election cycle, and the percentage of seats received by those parties respectively, is at its narrowest margin in at least the last seven decades.

While no party is entitled to a proportional share of their seats in Congress based on the proportion of cumulative votes they received nationally, examining the relative imbalance along these measures across redistricting cycles gives an indication of the extent to which political parties are benefiting from the district lines that are being drawn each decade.

Smart Politics examined the proportional allocation of Democratic and Republican seats each election cycle vis-à-vis their respective two-party cumulative vote share against the actual number of seats won by each party. These cycle-by-cycle results were then averaged across each redistricting period.

For example, in 2008, the Democrats won a cumulative 55.5 percent of the two-party vote in U.S. House races, with Republicans at 44.5 percent. If Democrats had been allotted a 'proportional' 55.5 percent share of U.S. House seats, they would have won 242 seats, or 15 seats fewer than the 257 they won on Election Day. Similarly, the GOP would have won 15 more seats and reached 193 seats instead of the 178 they won that November. In short, there was a 15-seat 'imbalance' in favor of the Democrats.

And how have the nation's current district lines fared since 2002 when stacked up against those drawn in past decades?

Through the first four election cycles since new district lines were introduced in 2002, the number of U.S. House seats per election cycle that disproportionately favored one party or the other has averaged seven seats: +1 seat in favor of the GOP in 2002, +9 seats for the GOP in 2004, +2 seats for the GOP in 2006, and +15 seats for the Democrats in 2008.

This seven-seat disparity is the lowest across the seven decades under analysis, and marks the third straight decade of a 'tightening' in the relationship between the total votes casts for U.S. Representatives for each major party in the 435 districts across the nation and the distribution of those 435 seats to each of those parties.

The biggest discrepancies across the decades occurred during the 1972-1980 redistricting period, when there was an average 31-seat imbalance each cycle (to the benefit of the Democratic Party every time). Democrats enjoyed a +13 seat advantage against the Republicans with regard to their share of the two-party vote in 1972, rising to +36 seats in 1974, +45 seats in 1976, +40 seats in 1978, and +19 seats in 1980.

The average difference between the proportional number of U.S. House seats allocated based on two-party vote share and the actual number of seats won decreased to 25 seats per cycle during the 1982-1990 redistricting period, to 10 seats per cycle during the 1992-2000 period, and to just 7 seats per cycle during the current period beginning in 2002.

Difference between U.S. House Seats Won by Party and Allocation of Seats by Proportional Two-Party Vote Share by Redistricting Period, 1942-2008

Period

Total seats per period

Average seats per cycle

2002-2008

28

7

1992-2000

51

10

1982-1990

125

25

1972-1980

154

31

1962-1970

141

28

1952-1960

82

16

1942-1950

93

19

Table reflects the difference in U.S. House seats won by party on Election Day and how those seats would be allocated if based on the proportional two-party share of votes cast for U.S. Representatives (less any seats won by independent or third-party candidates and any vacancies on Election Day). Data compiled by Smart Politics.

Of course, this is not to suggest attempts at gerrymandering of Congressional Districts have disappeared in statehouses across the country, nor that there are not individual instances of district lines being drawn to benefit one party or the other.

However, what one can conclude, is that either the frequency and impact of gerrymandering has decreased in recent years, or, unlike decades past, the gerrymandering that does exist has found a way to 'even itself out' across the nation's 435 districts so that there has been a substantial decrease in the extent to which one party has benefited from the creation of these district lines.

1 Comment

I wonder if there is an archive somewhere (without having to buy all of the Almanac of American Politics books or like series, they're expensive) of what the maps were for each state through the 1940's to physically look at the lines just for fun.

What's interesting is looking at the swing each cycle compared to the rest of the cycles in that mapping unit. 24-seat from GOP high to Dem high in the 2002-2008, but in the 70's, the shift was 26, making the two much more in parity of when elections go sour, how did your maps hold up.

Collin Peterson remarked last month that he is leaning to run for reelection to Minnesota's 7th Congressional District in 2016. If he does and is victorious, he will creep even closer to the top of the list of the longest-serving U.S. Representatives in Minnesota history. The DFL congressman is only the sixth Minnesotan to win at least 13 terms to the U.S. House of the 135 elected to the chamber in state history. Peterson trails 18-term DFLer Jim Oberstar (1975-2011), 16-term Republicans Harold Knutson (1917-1949) and August Andresen (1925-1933; 1935-1958), and 14-term DFLers Martin Sabo (1979-2007) and John Blatnik (1947-1974). Andresen died in office, Sabo and Blatnik retired, and Knutson and Oberstar were defeated at the ballot box in 1948 and 2010 respectively. At 70 years, 7 months, 11 days through Monday, Peterson is currently the ninth oldest Gopher State U.S. Representative in history. DFLer Rick Nolan of the 8th CD is the seventh oldest at 71 years, 1 month, 23 days.

Congressman Nick Rahall's failed bid for a 20th term in West Virginia this cycle, combined with a narrow loss by Nick Casey to Alex Mooney in Shelley Moore Capito's open seat, means that West Virginia Democrats will be shut out of the state's U.S. House delegation for the first time in over 90 years. The Republican sweep by two-term incumbent David McKinley in the 1st CD, Mooney in the 2nd, and Evan Jenkins over Rahall in the 3rd marks the first time the GOP has held all seats in the chamber from West Virginia since the Election of 1920. During the 67th Congress (1921-1923) all six seats from the state were controlled by the GOP. Since the Election of 1922, Democrats have won 76 percent of all U.S. House elections in the Mountain State - capturing 172 seats compared to 54 for the GOP.